The invention relates to a device for manufacturing a groove bearing having a bearing shaft and a bearing bush with cooperating bearing surfaces, of which at least one bearing surface is formed with at least one pattern of pumping grooves. The device comprises a bearing part and a cage which has one or more annular patterns of holes which are concentric with the pin or sleeve and which are engaged by hard balls which project from the cage and bear against a bearing surface of the bearing part. The bearing part and the cage are rotatable relative to each other. The bearing part may be a hard pin around which, or a hard pin in which, the cage is arranged.
The invention further relates to a method of manufacturing a groove bearing.
The device defined above and a method to be carried out by means of the device are known from EP-A 0,002,292, herewith incorporated by reference. The prior-art device is suitable for carrying out a method of manufacturing a hydrodynamic groove bearing comprising a bearing shaft and a bearing bush, which form cooperating surfaces, of which at least one surface is formed with at least one pattern of shallow lubricant pumping grooves. Such a hydrodynamic bearing is described in, for example, GB-A 1,022,391 and in GB-A 1,163,018, herewith incorporated by reference.
The prior-art device comprises a hard pin around which, or a hard sleeve in which, a cylindrical cage is arranged which has one or more annular patterns of holes which are arranged symmetrically about the central axis of the cage and which are engaged by hard balls having a diameter larger than the wall thickness of the cage. The cage and the pin or sleeve are each coupled to a drive arrangement capable of impressing a translation and a rotation upon the cage and the pin or sleeve. Thus, in carrying out the prior-art method the assembly comprising the pin or sleeve, the cage including the balls is translated and rotated relative to a bearing bush and a bearing shaft respectively, the balls bearing against the pin or the sleeve and being impressed into the softer material of the bearing bush and the bearing shaft respectively to form grooves therein.
It has been found that in carrying out the prior-art method the pin or the sleeve of the prior-art device is subjected to substantial wear as a result of large Hertzian stresses produced at the contact surfaces between the pin or sleeve and the balls. The wear manifests itself particularly as deformations of the pin or sleeve surfaces facing the cage, so that the contact surface of the pin or the sleeve becomes irregular, resulting in an inaccurate groove depth. In addition, this leads to a substantial wear of the balls.